Thermoplastic polymer compositions which are electrically insulating tend to accumulate very high electrostatic potentials via triboelectric generation and therefore are disadvantageous for use in many applications. For example, when such compositions are employed in electronic equipment, the static electric charge can accumulate and permanently damage sensitive integrated circuits if one or more parts formed of the electrically insulating polymer compositions are grounded through the integrated circuits.
Accordingly, resin compositions which exhibit antistatic properties and dissipate electrostatic charge are advantageous for use in various applications in the electronics industry including devices employing integrated circuit components, housings for computer components and other electrical equipment, smoke detectors which employ electrically polarized ionization chambers, and the like. Antistatic resins have been prepared by including one or more antistatic additives in the resin compositions. Generally, these additives are derivatives of quaternary ammonium salts and contain thermally unstable, hygroscopic functionalities such as polyethylene oxide radicals. The use of the hygroscopic groups is based on the theory that the antistatic effect is provided by a conductive surface layer on the resin which is formed from a water solution of organic ions. Resins having antistatic properties generally exhibit a static decay time of less than two seconds as required by Military Specification MIL-B-81705B when measured by Federal Test Method 4046, Standard 101B, employing an ETS Static Decay Meter, Model SDM 406B.
Generally, however, it has been difficult to provide antistatic properties to high performance engineering resins such as polyphenylene ether resin compositions since such resins are processed at relatively high temperatures which degrade conventional antistatic additives.